The basics of how to start modeling
For a very, very quick start. The absolute 3 things you need to know to begin effectively modeling in Blender are:


Interaction Modes


Object Mode

You are placed in object mode by default when you add a new primitive. You can translate, rotate and scale the object along the three axes whilst in this mode but to get finer control, you want to enter edit mode. Use Tab to enter edit mode from object mode.


Edit Mode

In edit mode, you have access the underlying structure of the object, you have much more control here and this is where you will spend most of your time when modeling. Likewise, use Tab to exit edit mode and enter object mode.    



Mesh Select Modes

Once you are in edit mode, you have 3 different control handles that you can use to help shape the mesh. These are pretty intuitive so I won't explain them and you can read more about these on the relevant wiki page.


Vertex


Edge


Face



Mesh manipulation

This is how you can shape and tweak your mesh. While you can do this object mode as well, you have much more control while you are in edit mode as you have access to the mesh control points.


Translate


Rotate


Scale





If you can understand those, you are on your way. Once you are past this stage, you can start looking at more advanced things such as extrusion, beveling and modifiers etc.

There is too much information to go into here and this should suffice. Your next steps would be to:


Watch some introductory video tutorials (archived), more tutorials for modeling in Blender.
Read the introduction to modeling on the manual.
Browse the modeling and workflow tags on this site for more tips and tricks such as this.


Also, some common shortcuts that you should learn are:


G to grab (translate)
S to scale
R to rotate


Nail these basics and you will be making your own models in no time, using the basic steps above, you can make your train tracks easily by just scaling and translating simple cubes.